TypeError: "listener" argument must be a function Error in node js eventemitter | Learning Curve- Perfect Tutorial for the beginers

var events=require('events');
var eventEmitter=new events.EventEmitter();

eventEmitter.on('datareceived',myhandler);
var myhandler=function hello()
{
console.log('data received successfully');
}
eventEmitter.emit('datareceived');

var events=require('events');

var eventEmitter=new events.EventEmitter();

eventEmitter.on('datareceived',myhandler);

var myhandler=function hello()

{

console.log('data received successfully');

}

eventEmitter.emit('datareceived');

while executing the above code it is thowing error-TypeError: “listener” argument must be a function

Solution:this is because of the code executing sequence.if we use emit() function at the bottom, then eventemitter.on() and other function should be above.

var events=require('events');

var eventEmitter=new events.EventEmitter();
var myhandler=function hello()
{
console.log('data received successfully');
}

eventEmitter.on('datareceived',myhandler);

eventEmitter.emit('datareceived');